He does intend to convey something real and nontrivial (well, some people might find it trivial, but enough people don't that it is important to be explicit) by saying that he is not a meta-ethical realist. The basic idea is that, while his brain is the causal reason for him wanting to do certain things, it is not referenced in the abstract computation that defines what is right. To use a metaphor from the meta-ethics sequence, it is a fact about a calculator that it is computing 1234 * 5678, but the fact that 1234 * 5678 = 7 006 652 is not a fact about that calculator.

This distinguishes him from some types of relativism, which I would guess to be the most common types. I am unsure whether people understand that he is trying to draw this distinction and still think that it is misleading to say that he is not a moral relativist or whether people are confused/have a different explanation for why he does not identify as a relativist.